Well, I am somewhat closer to enlightenment after chatting with Rob Cude on IRC.
The test has nothing to with the ability to permanently magnetize the object tested. Rather, the test seems to measure the effect of the object on a magnetic field.
This is what is confusing, as most people think that only Fe can be magnetized. Actually, some 'rare earth' magnets are much more powerful than Fe magnets. One such compound is Samarium Cobalt (SmCo), used in expensive stereo speakers.
Cobalt by itself may or may not be able to be magnetized permanently (I have differing data). This is not really relevant, however, as what quality we are measuring is the ability to create eddy currents in a magnetic field. Copper (Cu) is very good at doing this; old auto generators were Cu armatures rotating in a permanent magnetic field. This generated eddy currents, which created electricity. Copper cannot be permanently magnetized.
Some plastics are able to conduct electricity; these have had Co added! This may explain how some plastic items fail the test of whether or not magnetic mines will be affected by the object in question.
Rob said that the units used to determine whether or not an object was safe to use around magnetic ordnance were milioerstads; an acceptable measurement was 0.05 milioerstads, or 5 Gamma.
Oerstads, as it happens, I know to be units which measure an object's coercivity. Coercivity is usually defined as the strength of the magnetic field necessary to change existing magnetic domains. Actually, all of you know this already; magnetic tape is erased by a magnetic field before re-recording. Metal tape has a higher coercivity, which means a stronger magnetic field is necessary to erase it, compared with ferric oxide tape. This also means that the metal (Type IV) audio tape is more resistant to accidental degradation (such as placing the tape next to a speaker, with the strong permanent magnet inside), as again, it takes a stronger magnetic field to change the existing magnetic domains.
Rob further said that the object tested was tested at different distances from the measuring device. From 4 feet to one inch, then in contact with the measuring device.
Trying to make sense out of all these data, I believe what is being tested is the ability of an object to generate eddy currents in a magnetic field. This is certainly consistant with what I have read about magnetic mines, which depend on a disturbance in the earth's magnetic field to be triggered. Eddy currents are certainly magnetic fields which disturb the earth's magnetic field.
Note that neither a pre-existing magnetic field, nor an ability to create a permanent magnetic field in a given substance is required for that substance (Cu for example) to be an excellent eddy current generator.
As always, any input, comments, or criticisms are welcome, as I am still groping through the fog to really understand this. Walt Welch